Seasonal changes in nocturnal prolactin secretion and their relationship with melatonin secretion were monitored in wild (Mouflon, Ovis gmelini musimon) and domesticated sheep (breed Manchega, Ovis aries). Two groups of eleven adult females each, were maintained outdoors under natural photoperiod. Plasma concentrations of prolactin and melatonin were determined during the summer and winter sols...

Seasonal differences in suicide birth rates among Alaska Natives and for populations at different latitudes (residents of the Yukon, Saskatchewan, Montana, Wyoming, and Pennsylvania) were investigated. Seasonal birth rates for the general population were similarly examined. Suicide birth rates showed small seasonal variations for Alaska Natives with summer births showing more suicides. However,...

In nature Siberian hamsters utilize the decrement in day length following the summer solstice to implement physiological adaptations in anticipation of the forthcoming winter, but also exploit an intrinsic interval timer to initiate physiological recrudescence following the winter solstice. However, information is lacking on the temporal dynamics in natural photoperiod of photoperiodically regu...

Ionograms from a standard vertical-incidence ionosonde chain (nine stations), obtained over a wide range of southern latitudes (in geom.lat. range: 23–52 S), were digitally scanned at 5-min intervals at nighttime (18:00– 06:00 LT) for 13 months (January 2004–January 2005). An important parameter of the F-region, so-called range spreadF (Sr), was for the first time quantified in km. Maximum in S...

The quasi 2-day wave is known as a strong dynamic perturbation occurring usually after solstice in the middle and upper atmosphere. The excitation mechanism of this transient wave is discussed for years but no clear answe] has been altained. In this paper, propagating characteristics of the 2-day wave are studied based on 8-month temperature measurements from the Microwave Limb Sounde~ (MLS) on...

Alpine and northern treelines are primarily controlled by low temperatures. However, little is known about the impact of low soil temperature on tree transpiration at treelines. We aim to test the hypothesis that in cold-limited forests, the main limiting factors for tree transpiration switch from low soil temperature before summer solstice to atmospheric evaporative demand after summer solstic...

We investigated if absolute (nocturnal) or relative (nocturnal/diurnal ratio) plasma melatonin concentrations were associated with the seasonal ovulatory activity in Ile-de-France ewes. Ninety-six and 121 ewes in two different groups of the same flock were used to determine the potential existence of a relationship between melatonin concentrations at the summer and winter solstices, and the dat...

Solar irradiance (W/m2) and downwelling diffuse attenuation coefficients (Kd; 1/m) were determined in several locations in Prince William Sound (AK, USA) between April 2003 and December 2005 to assess temporal and spatial variation in solar radiation and the risks of photo-enhanced toxicity from spilled oil. Weekly irradiance measurements of surface visible light, ultraviolet B (UVB), and ultra...

Circadian rhythms reflect extensive programming of biological activity that meets and exploits the challenges and opportunities offered by the periodic nature of the environment. In the present investigation, we recorded the total activity of athletic horses kept at four different times of the year (vernal equinox, summer solstice, autumn equinox and winter solstice), to evaluate the presence o...